 .block-box :first-child {
     width: 200px;
     height: 100px;
     margin: 15px;
     padding: 15px;
     border: 3px solid black;
     overflow: scroll;
 }
 
 .inline-box :first-child {
     width: 200px;
     height: 100px;
     /*无用*/
     margin: 15px;
     padding: 15px;
     border: 3px solid red;
 }
 
 .normative-box {
     width: 350px;
     height: 150px;
     margin: 25px;
     padding: 25px;
     border: 5px solid black;
 }
 
 .box {
     width: 400px;
     height: 50px;
     margin: 15px;
     padding: 15px;
     border: 3px solid green;
     background-color: teal;
 }
 /*所有的盒子的CSS*/
 
 .pos_static {
     position: static;
     background-color: aqua;
 }
 
 .pos_relative {
     position: relative;
     background-color: red;
     top: -15px;
     left: -100px;
 }
 
 .pos_fixed {
     position: fixed;
     background-color: blue;
     top: 0px;
     right: 10px;
     z-index: 2;
 }
 
 .display:hover+div {
     display: block;
     border: 150%;
 }
 
 .pos_absolute {
     position: absolute;
     background-color: burlywood;
     top: 1125px;
     left: 10px;
     display: none;
 }
 
 .pos_sticky {
     position: -webkit-sticky;
     position: sticky;
     top: 0;
     padding: 5px;
     background-color: #cae8ca;
     border: 2px solid #4CAF50;
 }
 
 .float {
     float: left;
     margin-left: 20px;
 }
 
 .unfloat {
     margin-left: 400px;
 }
 
 .clf {
     clear: both;
 }